Panasonic AG-HPX300 Broşür ve Teknik Özellikler - Sayfa 9
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Sayfayı YazdırSelectable DVCPRO HD Recording
The AG-HPX300 also supports the conventional DVCPRO HD codec.
Because the AG-HPX300 is designed to be used with the AG-HPX170/
HVX200A or a DVCPRO HD VTR, it adapts to a variety of system
configurations.
Sample Images of Intraframe Preduction
Intra-Frame (I-Frame Only ) Compression Superiority
Motion-image compression can be divided roughly into two methods: AVC-Intra
and DVCPRO HD use I-Frame Only compression, while HDV uses Long GOP
compression.
The MPEG-4 AVC/H.264 standard family encompasses both. At the AVCHD end
of the standard it utilizes the Long GOP for the advantage of longer record
times, and at the upper end where the HPX300 is, it utilizes the I-Frame only.
When the images of adjacent frames are similar, Long GOP compression
achieves an advantageously low bit rate. However, this trait is not often seen in
broadcasts like flash-filled press conferences, fast-action sports, and video with
rapid move and electronic displays. Also, because processing is performed
frame-by-frame in I-Frame Only , new-generation multi-core CPUs offer high-
speed parallel processing. This makes I-Frame Only compression more suitable
for nonlinear editing than Long GOP, for which parallel processing is difficult due
to its inter-frame dependence. With its I-Frame Only compression, AVC-Intra
produces remarkably stable images that are unaffected by adjacent frames,
and meets professional needs in virtually all situations and workflows.
A V C - I N T R A T E C H N O L O G Y
Left: Original image Center: Intra-frame predictive image Right: Difference image obtained from subtracting the
intra-frame predictive image from the original image. This shows the high accuracy of intra prediction.
For further information about MPEG-4 AVC/H.264, including an explanatory video,
please visit: https://eww.pavc.panasonic.co.jp/pro-av/technology/
48-kHz/16 bit, 4-Channel Digital Audio
The AG-HPX300 can record full 48-kHz/16 bit digital audio on all four
channels. You can freely select the audio source for each channel, choosing
from mic-in, line-in and wireless receiver.
Twice the Compression Efficiency of MPEG-2
By selecting the most effective compression techniques from among those in
compliance with the H.264 standard, AVC-Intra has doubled the compression
ratio of MPEG-2, even with I-Frame Only compression. Its intraframe predictive
and context-adaptive entropy coding are particularly effective methods for
boosting compression efficiency.
Intraframe predictive coding (intra prediction)
This process generates predictive images based on adjacent blocks of 8 x 8
pixels. Selecting the most suitable predictive mode from among nine luminance
signal modes (see illustration) and four color signal modes, it generates accurate
predictive images. The residual data (obtained by subtracting a predictive image
from the original input image) is recorded together with the predictive image.
Because the prediction accuracy is high, there's minimal residual data, and thus
high compression is achieved. This process is conducted within the frame, so
prediction accuracy remains high even with fast-motion images.
Average
mode 0
mode 1
mode 2
mode 4
mode 5
mode 6
Adjacent pixels
Predictive pixels
Copy of below pixel
mode 8
Context-adaptive entropy coding
The entropy coding process used in MPEG-4 AVC/H.264 utilizes CAVLC
(Context Adaptive VLC) and CABAC (Context Adaptive Binary Arithmetic
Coding), both of which are context adaptive. MPEG-2 uses a fixed table when
performing the VLC coding, with the result that compression efficiency is low
with some types of images. In context-adaptive coding, on the other hand,
operation varies with different kinds of images and high compression efficiency
is maintained at all times.
mode 3
mode 7